High-frequency electric discharge device



Sept. 2, 1947. D. A. WILBUR ETAL HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE rim; Dec. 11, 1944 Invent ors 1& E m W0 AR MD a nb mw L by MT/JMZW Their Attofney Eatentecl Sept. 2, 194'? 2,426,655 7 HIGH-FREQUENCY ELECTRIC DISCHARGE DEVICE Donald A. Wilbur, Troy, and Louis D. Roberts, Schenectady, N. Y, assignors to General Elec tric Company, a corporation of New York Application December 11, 1944, Serial No. 567,556

14 Claims. (01. 250 27.5)

Our invention relates to high frequency electric discharge devices and more particularly to improved high frequency devices of the magnetron type.

Magnetrons of the split-anode type have been employed as oscillators in the moderately high frequency range, for example, from 1 to 400 me acycles. When operating in the lower portion of this frequency range, the power handled by the device has been quite limited due to heating and destruction of the seals between the high frequency conductors associated with the anode segments and the enclosing envelope or with destruction of other portions of the envelope. We have found that the power handled by devices of this character may be materially increased if electrons from the interelectrode space are prevented from bombarding the region of the seals about the high frequency lead-in conductors. In accordance with the teachings of our invention, we provide an improved magnetron construction in which the escape of electrons from the interelectrode space is minimized and in which the escaping electrons are prevented from reaching the seals about the high frequency lead-in conductors.

It is an object of our invention to provide a new and improved electric discharge device of the magnetron type.

It is another object of our invention to provide a new and improved magnetron construction in which bombardment of the seals about the high frequency conductors is effectively eliminated.

In one illustrated embodiment of our invention, a magnetron device of the split-anode type is provided with shields mounted on the anode members and arranged with respect to the gaps between the anode members so that any electrons escaping from the interelectrode space through the gaps must travel in a zigzag path. This minimizes the escape of electrons duringthe portion of the high frequency cycle that the high frequency voltage is lower than the cutoff voltage of the gaps of the device. In order to protect the seals from the electrons which do escape from the interelectrode space, annular disks or shields of molybdenum, or other material which is a poor secondary emitter, are supported in insulated relation about the high frequency leadin conductors. These shields become electrostatically charged due to the collection of electrons thereon and are effective to force the remaining electrons which have escaped from the interelectrode space and are traveling towards the region of the seals to be collected on the high frequency conductors.

In accordance with another illustrated embodiment of our invention, we provide a shielding enclosure in the form of a rectangular box which totally encloses the interelectrode space of the 2 device. The walls of the box are provided with openings. through which the anode members and the cathode may pass in spaced relation with respect to the walls of the openings. The enclosure is supported in insulated relation with respect to the electrodes so that the shield may become negatively charged as electrons are collected.

For a better understanding of our invention, reference may be had to the following description taken in connection With the accompanying drawing in which Fig. 1 is a perspective view of one embodiment of our invention; Fig. 2 is a detailed View showing the construction of one of the shields secured to the high frequency leadin conductors, and Fig. 3 is a perspective view of a modification of our invention.

Referring now to Fig, 1 of the drawing, we have shown our invention embodied in a magnetron device including a generally cylindrical evacuated envelope I preferably formed of glass. The envelope encloses an anode structure comprising two anode members 2 and 3 having semi-cylindrical faces arranged in opposed relation to provide a circular array. As illustrated in the drawing, the members 2 and 3 are mounted in mutually spaced relation to provide gaps 1i and 5 between them and are, respectively, supported by parallel conductors 6 and l which extend through one end of the envelope. The conductors 6 and 1 may to advantage be formed of copper tubing and are sealed through the end wall of the envelope l by suitable seal constructions which may include a fernico shoulder or sleeve 8. v

A source of electrons in the generally annular space definedby opposed ends of members 2 and 3 is provided by an elongated cathode 9 which may be a tungsten wire, either uncoated or coated with a suitable electron emissive oxide. The cathode is supported symmetrically between the 'curved surfaces of anode members 2 and 3 by lead-in conductors l0 and II which are sealed through the base of the envelope I to provide externally accessible terminals 12 (only one of which is visible on the drawing) for a source of heating current. One of the terminals may also be connected to a source of high negative direct current voltage if the anode is to be operated at ground potential. Suitable end plates or shields l3 are mounted opposite the open ends of the interelectrode space to minimize the escape of electrons, and these shields may each be supported from one of the cathode lead-in conductors, such as conductor ID, by a wire bracket It. A metallic tab {5 carrying a suitable getter material may also be supported in the envelope by a Wire l6 supported from the lead-in conductor I0.

During the portion of the high frequency voltage cycle that the voltage is less than the cutoff voltage of the gaps of the device electrons have V to the shield 21.

a tendency to escape from the gaps between the opposed ends of the anode members 2 and 3.

To minimize the escape of these electrons, we

provide shield members I1, l8, l9 and 20 supported from the anode members 2 and 3 and arranged to require any electrons escaping from the gaps 4 and 5 to travel in a circuitous or zigzag T path. As illustrated, the shield members are formed of material which is a'poor secondary a loading: characteristics.

. previously the gaps 4 and 5, respectively, while the shield members I8 and 19 are spaced further from the surfaces of the anode members and have the end portions "thereof in alinement with or in overlapping relation with the end portions of the shields I1 and 20, thus requiring the electrons escaping from gaps 4 and 5 to travel in a zigzag path and greatly increasing the likelihood that the electrons will be collected.

In order to prevent electrons escaping from the interelectrode space from bombarding the seals between envelope l and conductors B and I, we provide on the conductors 6 and] between the anode members 2 and 3 and the seals with the envelope l suitable shields in the form of metallic disks 2 I. As is best illustrated in Fig. 2, the disk 2| is supported on the upper end of an insulating cylinder 22 which is supported on the conductor 6 in any suitable manner. As illustrated, the cylinder is supported by awire bracket 23 having one portion secured to the conductor 6 and another portion engaging the cylinder 22. In a similar manner, disk 2| is secured inposition on the upper end of the cylinder 22 by. a wire bracket 24 having. one or more struts 25. secured The shield on conductor 1 is 'of the same construction. During operation of the device, the disks 2| become charged nega tively by the collection of electrons and are efiective to compel electrons which escape from the interelectrode space to move to conductors 6 and I and be collected. v

For the sake of simplicity, the source of magnetomotive force which is impressed across the anode of the device in a direction parallel to the elongated cathode 9, as indicated by the arrow in. Fig. 1, hasnot been illustrated. It will also be understood that the frequency of operation of the device is determined by a short circuiting con- In the operation of the illustrated embodiment of our invention, electrons emitted from the cathode 9 travel in a curvilinear path in the interelectrode space under the action of the resultant action of an electric field resulting from a direct current voltage impressed between the cathode and the anode members and-a magnetic field produced in the interelectrode space in a direction parallel to the elongated cathode member. Electrons tend to escape from the gaps 4 and 5during that portion of the high frequency cycle that the high frequency voltage is less than the c-utofi voltage of the gaps of the device. The cutoif voltage may be reduced by reducing the width .of

the gaps, but at the expense of increasing the capacity between the anode members. In the electrons escaping from the gaps to travel a circuitous path to minimize the number of escaping electrons without appreciably increasing the' capacity between the anode members which.

would result from the reduction in the width of the gaps 4 andE. The reduction in gap width also decreases efiiciency and has a detrimental effect on certain electrical characteristics such as the The metal shieldmembers 2| which surround the high frequency leads 5 and l are formed of material which is a poor secondary emitter to prevent the liberation of secondary electrons; These shield members, as stated, become electrostatically charged during operation of the device by the collection'of some electrons and operate to force other electrons to be collected by conductors 6 and l which would otherwise bombard the seals between the high frequency conductors 6 and l and the envelope 1. p

It is a characteristic of shield members employed in accordance with our invention that they have an extended area in a plane perpendicular or at least at a. substantial angle with the direction of the magnetic field of the device.

The modification of our invention illustrated in Fig. 3 is in general similar to the modification of Fig. 1, and the same reference numerals have been used to designate corresponding parts. 1t will be noted that the relative dimensions of the parts in the arrangement of Fig. 3 are different, resulting from the different shielding arrangement employed. For example, the envelope l is considerably shorter than the envelope of Fig. 1 and the parallel conductors supporting the anode members are considerably shorter. This improves the operationof the device with respectjto the magnitude of the frequencies attainable.

Referring now to,Fig.. 3, the interelectr'ode space defined by the elongated cathode 9 .andthe V opposed surfaces of theanode members 2. and 3 issubstantially totally enclosed by a box-like structure 26. As illustrated in the drawing,.this

structure is substantially rectangular and has openings 2"! centrally located. in' opposite walls to receive the cathode 9; The walls of the encloenclosure 26is supported in thedesired relationspring memberjSZ for tensioning the cathode 9 V is also visible in Fig. 3. l.

The operation of the 'embodimentjillustrated in Fig. 3 is believed tobe apparent from the detailed description of the operation of the embo d-' iment illustrated in Fig; l. The totalenclosure provided in Fig. 3 practically precludes any.v electrons which escape from the interelectrode space from bombarding any portionlof the envelope and in this way materially increases the power obtainable from a device of given dimensions.

With magnetron constructions including. the

structural features of the illustrated embodiments of our invention, we have been "able to'opcrate at considerably higher power requirements without'experiencing any difiiculty from destruction of the seals about the high frequency conductors or any other portion of the envelope.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects, and we, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of ourinvention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said envelope adjacent saidsource of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, shield members substantially completely covering said gaps to force electrons escaping from said gaps to travel a circuitous path, lead-in conductors sealed through said envelope and connected with said anode members, and means including a metallic shielding structure supported in insulated relation with respect to said anode structure in the path of electrons traveling from said gaps to the region of the seals between said envelope and said conductors to force collection of electrons escaping from said gaps on said lead-in conductors and thereby to prevent electrons from bombarding the seals between said conductors and said envelope.

2. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said envelope adjacent said source of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, shield members substantially completely covering said gaps to force electrons escaping from said gaps to travel a circuitous path, lead-in conductors sealed through said envelope and connected with said anode members, and means including a metallic shielding structure surrounding each of said lead-in conductors and supported in insulating relation with respect thereto in the path of electrons traveling from said gaps to the region of the seals between said envelope and said conductors to force collection of electrons escaping from said gap on said lead-in conductors and thereby to prevent electrons from bombarding the seals between said conductors and said envelope.

3. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said envelope adjacent said source of electrons including a pair of mutually spaced anode members having opposed surfaces and defining between said surfaces a cylindrical space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on diametrically opposite sides of said cylindrical space charge chamber, shielding means for minimizing the escape of electrons from said gaps including a pair of angular members of conducting material substantially completely covering each of said gaps, each of said angular members in each said pair being supported from a different one of said anode members and having a portion extending toward the other of said angular members in overlapping relationship therewith over one of said gaps whereby said angular members cooperate with the anode structure to collect electrons passing through said one of said gaps, lead-in conductors sealed through said envelope and connected with said anode members, and means including a metallic shielding structure supported in insulated relation with respect to said anode structure in the path of electrons traveling from said gaps to the region of the seals between said envelope and. said conductors to force collection of electrons escaping from said gaps on said lead-in conductors and thereby to vprevent electrons from bombarding the seals between said conductors and said envelope.

4. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said en'- velope adjacent said source of electrons including a pair of mutually spaced anode members having opposed surfaces and defining between,

said surfaces a cylindrical space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on diametrically opposite sides of said cylindrical space charge chamber, shielding means for minimizing the escape of electrons from said gaps including a pair of angular members of conducting material substantially completely covering each of said gaps, each of said angular members in each said pair being supported from a different one of said anode members and having a portion extending toward the other of said angular members in overlapping relationship therewith over one of said gaps whereby said angular members cooperate with the anode structure to collect electrons passing through said one of said gaps, lead-in conductors sealed through said envelope and connected with said anode members, and means including a metallic shielding structure surrounding each of said lead-in conductors and supported in insulated relation with respect thereto in the path of electrons traveling from said gaps to the region of the seals between said envelope and said cons ductors to force collection of electrons escaping from said gaps on said lead-in conductors and thereby to prevent electrons from bombarding the seals between said conductors and said envelope.

5,.A magnetron device adapted to have highpower output comprising an envelope, a source of electrons, an anode structure within said onvelope adjacent said source of electrons, including mutuall spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, lead-in conductors sealed through said envelope and connected with said anode members, and means including a metallic shielding structure supported in insulated relation with respect to said anode structure in the path of electrons traveling from said gaps to the region of the seals apaaoee between said envelope and said'conductors to force collection of electrons escaping fromsaid gaps onsaid lead-in conductors and thereby to prevent electrons frombombarding the seals between said conductors and said envelope.

6. A magnetron device adapted to have highpower output comp-rising an envelope, a source of electrons, an anode structure within said envelope adjacent said source of electrons including a pair of mutually spaced anode members having opposed surfaces and defining'between said surfaces a space charge chamber within which electrons constitutingthe space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, leadin conductors sealed through said envelope and connected with said anode members, and metallic shielding means surrounding each of said leadin conductors and supported in insulated relation with respect thereto in the path of electrons trav eling from said gaps tothe region of the seals between said envelope and said conductors to force collection of electrons escaping from said gaps on said lead-in conductors and thereby to prevent electrons from bombarding the seals between said conductors and said envelope.

7. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure'within said envelope adjacentsaid source of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, shielding means for minimizing the escape of electrons from said gaps including a pair of angular members of conducting material substantially completely covering each of said gaps, each of said angular members in each said pair being supported from a different one of said anode members and having a portion extending 1m toward the other of said angular members in overlapping relationship therewith over one of said gaps whereby said angular members cooperate with the anode structure to collect electrons passing through said one of said gaps.

8. A magnetron device adapted to have high power output comprising an envelope, a source .of electrons, an anode structure within said envelope adjacent said source of electrons including a pair of mutually spaced anode members 'shaped members of conducting material substantially completely covering each of said gaps, each of said L-shaped members in each said pair being supported from a different one of said anode members by one arm and having the other arm extending toward the other of said L-shaped members in overlapping relationship with the other arm thereof over one of said gaps whereby said L-shaped members cooperate with the anode structure to collect electrons passing through said-one of saidgaps 1 A r i trons from said gaps including a pair of shield members of conducting material substantially completely covering each of said gaps, 'eachof said shield members ineach said pair being sup-'- ported from a diiferent one of said anode members and having a portion extending toward the other of said shield members in overlapping rela tionship therewith overone of said gaps where by said shield members cooperate with the anode structure to collect electrons passing through said one of said gaps Y 10. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said envelope adjacent said source of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, lead in conductors sealed through said envelope and connected with said anode members, and

means in the path of electrons traveling from said gaps to the region of the seals between said envelope and said;cond-uctor for forcing collection-of electrons escaping from said gaps on said conductors comprising an insulating cylinder secured to and surrounding each said conductor' between said envelope, and said anode members, and an apertured metallic disk surrounding each said conductor and supported from each said-ccylinder in insulated relationship tosaid conductor. a

11. A magnetron device adapted to-have high power output comprising anenvelope, a source of electrons, an anode structure within said: envelopead'jacent said source of electrons includingmutually spaced anod e members having opposed surfaces and defining between said sur-' faces a cylindrical space charge chamber within which electrons constituting the space" charge of the device are adapted to move, said anode membersalso defining between said surf aces gaps conductors comprising an insulating cylinderseductor.

located on the periphery of said space charge chamber, parallel lead-in conductorssealed through said envelope by glass' to metal sea-ls and terminating in said a-node "members, and

means in the path iof electrons traveling from said gaps to the region of the seals between said envelope and said conductor for forcing collec-' tion of electrons escaping from said gaps on said cured to and surrounding each'said conductor between said envelope and said anode members, and an apertured metallic disk surrounding each said conductor and supported'from each said,

insulated relationship to said con 7 cylinder in ,12; A magnetrondevice adapted tohave high velope adjacent said source of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, and a shielding structure supported in insulated relation with respect to said anode structure for preventing electrons escaping from said space charge chamber from bombarding said envelope, said shielding structure comprising a hollow metallic enclosure substantially totally enclosing the portions of said anode structure defining said space charge chamber.

13. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said envelope adjacent said source of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, and a shielding structure supported in insulated relation with respect to said anode structure for preventing electrons escaping from said space charge chamber from bombarding said envelope, said shielding structure comprising a hollow metallic enclosure substantially totally enclosing the portions of said anode structure defining said space charge chamber.

14. A magnetron device adapted to have high power output comprising an envelope, a source of electrons, an anode structure within said envelope adjacent said source of electrons including mutually spaced anode members having opposed surfaces and defining between said surfaces a space charge chamber within which electrons constituting the space charge of the device are adapted to move, said anode members also defining between said surfaces gaps located on the periphery of said space charge chamber, lead-in conductors sealed through said envelope and connected with said anode members, and means in the path of electrons traveling from said gaps to the region of the seals between said envelope and said conductor for forcing collection of electrons escaping from said gaps on said conductors comprising a pair of shield members each surrounding a different one of said conductors, and means attached to each of said conductors for supporting said shield members in insulated relation with respect to said anode members.

DONALD A. WILBUR. LOUIS D. ROBERTS.

REFERENCES CITED The following references are of record in the file of this patent:

522,360 Great Britain June 17, 1940 

